Latch bolt mechanisms are utilized to retain a door in a closed position until it is intentionally opened. These latch bolt mechanisms frequently utilize cams to extend and retract the bolt. The cams may be actuated by rotary, lift, push, pull or trigger actuators. However, cam-operated latch bolt mechanisms can be complex, bulky and expensive to manufacture.
Push-pull-actuated latch bolts are known in the art for securing a door in a closed position until the latch bolt is moved to its retracted position by the pushing or pulling of a handle on one side of the door. As evidenced by U.S. Pat. No. 5,157,953 issued to Hung, such push-pull-type lock mechanisms can be quite complicated in their design and operation with many mating and interacting parts. They may, for instance, effectuate retraction of the latch bolt by means of a mating rib and groove combination on the latch bolt and spindle that require precise machining during manufacture, complicated installation processes, and result in increased wear during operation. See, e.g., U.S. Pat. No. 2,939,737 issued to Nygren, and U.S. Pat. No. 2,124,099 issued to Zagrzejewski.
Such a push or pull-actuated latch bolt also is often surface mounted to the interior side of a storm door, adjacent a main entrance door. As a result, the latch bolt mechanism hardware extends inwardly from the storm door and can interfere with the operation and/or closure of the main entrance door. These latches can also be somewhat unsightly. They may require a strike plate which would be visible even when the door is in a closed position. The strike plate may also interfere, or catch, a person who exits or enters through the doorway.
Some prior art latch bolt mechanisms have utilized a lock mechanism that slidably engages an inclined surface of the bolt so that when the latch bolt is locked in its extended position, and a force is applied inwardly on the bolt, the inclined surfaces of the bolt engage the inclined surface of the lock to cause the lock mechanism to slide to its unlocked position, thereby allowing retraction of the bolt. See U.S. Pat. No. 6,536,248 issued to Fan. However, this automatic unlocking feature defeats the purpose of a dead bolt lock, and makes the latch mechanism less secure.
Therefore, there is a need for a latch bolt mechanism that is: inexpensive to construct, compact in size with limited lateral projection to accommodate all door thickness applications and storm door use, simple in construction, and flexible in use with all types of actuators. There is also a need for a push-pull lock that functions as a true deadbolt lock and as a mortise push-pull latch bolt mechanism that is symmetrical for use on both right and left-handed doors without installer modification.